Pressure cycle downhole tool actuation

ABSTRACT

A pressure isolation assembly can include multiple pressure isolation modules arranged in series and isolating a pressure actuated downhole tool from a downhole fluid pressure. Each of the modules may be configured to open in response to a single pressure cycle comprising an increase in the downhole fluid pressure followed by a decrease in the downhole fluid pressure. A method can include determining a number of fluid pressure cycles to apply to enable actuation of a downhole tool; installing a number of pressure isolation modules in a pressure isolation assembly, the number corresponding to the number of pressure cycles; deploying the downhole tool and the pressure isolation assembly while the pressure isolation assembly isolates a fluid passage of the downhole tool from downhole fluid pressure; and applying the number of pressure cycles, thereby permitting communication of at least a fraction of the downhole fluid pressure to the fluid passage.

BACKGROUND

This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in at least one example described below, more particularly provides for actuation of a downhole tool with multiple pressure cycles.

A variety of different techniques have been developed over the years for actuating a downhole tool in a subterranean well. In some of those techniques, increased pressure can be applied to the downhole tool to thereby cause actuation of the downhole tool.

Therefore, it will be readily appreciated that advancements in the art of actuating a downhole tool in response to applied pressure are continually needed. It is among the objectives of the present disclosure to provide such advancements to the art. These advancements may be used with a variety of different downhole tools and in a variety of different types of well operations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative partially cross-sectional view of an example of a downhole tool assembly and associated method which can embody principles of this disclosure.

FIG. 2 is a representative partially cross-sectional view of an example of a well system and associated method in which the downhole tool assembly can be incorporated, and which can embody the principles of this disclosure.

FIGS. 3A & B are representative cross-sectional views of successive axial sections of another example of the downhole tool assembly which can embody the principles of this disclosure.

FIGS. 4A-C are representative cross-sectional views of an example of a pressure reduction device in a series of configurations over a downhole fluid pressure cycle.

FIGS. 5A-C are representative cross-sectional views of an example of a pressure isolation module in a series of configurations over the downhole pressure cycle.

FIG. 6 is a representative cross-sectional view of an example of the pressure isolation module in a pressure isolation assembly of the downhole tool assembly.

FIG. 7 is a representative cross-sectional view of the downhole tool assembly with a downhole tool thereof in an actuated configuration.

FIG. 8 is a representative cross-sectional view of another example of the pressure isolation assembly.

DETAILED DESCRIPTION

Representatively illustrated in FIG. 1 is a downhole tool assembly 10 and associated method which can embody principles of this disclosure. However, it should be clearly understood that the downhole tool assembly 10 and method are merely one example of an application of the principles of this disclosure in practice, and a wide variety of other examples are possible. Therefore, the scope of this disclosure is not limited at all to the details of the downhole tool assembly 10 and method described herein and/or depicted in the drawings.

In the FIG. 1 example, the downhole tool assembly 10 is connected in a tubular string 12. The tubular string 12 could be a casing, liner, segmented tubing, coiled tubing, pipe, drill, completion, stimulation, or other type of tubular string. In other examples, the downhole tool assembly 10 may not be connected in a tubular string.

As depicted in FIG. 1 , the downhole tool assembly 10 includes a pressure isolation assembly 14 and a pressure actuated downhole tool 16. The pressure isolation assembly 14 isolates the downhole tool 16 (or a portion thereof) from pressure in a downhole environment, until it is desired to actuate the downhole tool.

The downhole tool 16 may be any type of pressure actuated downhole tool. Examples of pressure actuated downhole tools include, but are not limited to, packers, valves, gravel packing equipment, stimulation equipment, directional drilling equipment, etc. The scope of this disclosure is not limited to use of any particular type of downhole tool in a downhole tool assembly.

In the FIG. 1 example, the pressure isolation assembly includes four pressure isolation modules 18 a-d connected in series. Any number of pressure isolation modules may be used in a pressure isolation assembly in keeping with the principles of this disclosure.

The pressure isolation modules 18 a-d prevent downhole fluid pressure (indicated by arrow 20) from being communicated to the downhole tool 16, until it is desired to actuate the downhole tool. As depicted in FIG. 1 , the fluid pressure 20 is delivered via an internal flow passage 22 of the tubular string 12 (such as, from a pump or other pressure source connected to the tubular string). In other examples, the fluid pressure (indicated by arrow 24) could be delivered via an exterior of the tubular string 12 (such as, in an annulus formed between the tubular string 12 and a wellbore or another tubular string (not shown) surrounding the tubular string 12). In further examples, the fluid pressure could be delivered via a sidewall of the tubular string 12, or via a capillary or control line. Thus, the scope of this disclosure is not limited to any particular technique for delivering the fluid pressure to the pressure isolation assembly 14.

As depicted in FIG. 1 , the pressure isolation modules 18 a-c block the flow passage 22 to thereby isolate the downhole tool 16 from the fluid pressure 20. In other examples, the flow passage 22 may extend through the pressure isolation assembly 14 and may extend through the downhole tool 16. Thus, one portion of the downhole tool 16 may be exposed to the fluid pressure 20 without regard to a configuration of the pressure isolation assembly 14, in which case the pressure isolation assembly may isolate another portion of the downhole tool (such as, an actuator) from the fluid pressure 20 until it is desired to actuate the downhole tool. In one example, the downhole tool 16 could be actuated by the fluid pressure 24 external to the tubular string 12, in which case the pressure isolation assembly 14 could isolate an internal portion of the downhole tool from the fluid pressure 24, until it is desired for the downhole tool to be actuated.

As mentioned above, the pressure isolation modules 18 a-d are connected in series in the pressure isolation assembly 14. In this example, the pressure isolation modules 18 a-d are all initially closed. The pressure isolation modules 18 a-d can be opened in succession (18 a first, then 18 b, then 18 c, then 18 d) in response to respective downhole fluid pressure cycles applied to the pressure isolation assembly 14 (such as, via the flow passage 22).

Thus, when a first fluid pressure cycle is applied the first pressure isolation module 18 a is opened, and when a second pressure cycle is applied the second pressure isolation module 18 b is opened, etc. When all of the pressure isolation modules 18 a-d have been opened, the downhole tool 16 can be actuated by the fluid pressure 20 delivered via the flow passage 22.

It will be appreciated that, by changing the number of the pressure isolation modules 18 a-d, a corresponding change to the number of pressure cycles required to communicate the fluid pressure 20 to the downhole tool 16 can be made. In this example, the number of the pressure isolation modules 18 a-d is equal to the number of pressure cycles required to communicate the fluid pressure 20 to the downhole tool 16, since each of the pressure isolation modules can be opened in response to application of a single pressure cycle to the pressure isolation module. In other examples, a pressure isolation module may be opened by application of multiple pressure cycles.

The pressure isolation modules 18 a-d are “modular” in that they are all the same or similarly configured for convenient selection and installation of varying numbers of the modules in the pressure isolation assembly 14. It may be desirable for different numbers of the pressure isolation modules to be used in corresponding different well operations. For example, in one well operation it may be desired for six pressure cycles to be applied to the pressure isolation assembly 14 before the downhole tool 16 is actuated, and in another well operation it may be desired for five pressure cycles to be applied before the downhole tool is actuated. The modular characteristic of the pressure isolation modules permits the number to be changed conveniently and without a need to produce and inventory separate pressure isolation assemblies for each corresponding number of desired pressure cycles.

In the FIG. 1 example, a pressure cycle used to open each of the pressure isolation modules 18 a-d consists of a single fluid pressure increase to a level greater than a predetermined pressure, followed by a single fluid pressure decrease to a level less than another predetermined pressure. The predetermined pressures could be the same, but in most examples the predetermined pressure for the pressure increase will be greater than the predetermined pressure for the pressure decrease.

As depicted in FIG. 1 , the pressure isolation assembly 14 is connected to, but separate from, the downhole tool 16. In other examples, the pressure isolation assembly 14 and the downhole tool 16 could be integrated (such as, by sharing a common outer or inner housing, etc.). Thus, the scope of this disclosure is not limited to any particular configuration of the pressure isolation assembly and the downhole tool.

Referring additionally now to FIG. 2 , an example of a well system 30 and an associated method are representatively illustrated. The FIG. 2 well system 30 and method utilize the downhole tool assembly 10. However, the downhole tool assembly 10 can be used in other well systems and other methods, in keeping with the scope of this disclosure.

As depicted in FIG. 2 , the downhole tool assembly 10 is connected in the tubular string 12. In this example, the tubular string 12 is a casing string used to line a wellbore 32. For clarity of illustration, only a single casing string is shown in FIG. 2 , but in actual practice multiple casing strings and perhaps liner strings may be installed in the wellbore 32.

The casing and/or liner strings may be cemented in the wellbore 32. In other examples, a section of the wellbore 32 in which the principles of this disclosure are practiced may be uncased or open hole. Thus, the scope of this disclosure is not limited to any particular details of the well system 30 as depicted in FIG. 2 or described herein.

In the FIG. 2 example, the downhole tool assembly 10 is used as an initially closed “toe” valve connected near a distal end of the tubular string 12 in a lateral section of the wellbore 32. It is desired in this example to be able to open the toe valve prior to conducting a stimulation operation (such as, acidizing, fracturing, etc.), using fluid pressure 20 supplied by a surface pump 34. However, the toe valve may be subject to application of one or more pressure increases during installation, cementing and pressure testing of the tubular string 12, and so it would be difficult to construct the toe valve so that it would not open when the tubular string is installed, cemented and pressure tested, but so that it would open when a subsequent pressure increase is applied.

The downhole tool assembly 10 solves this problem by requiring a selected number of pressure cycles to be applied prior to actuating the toe valve. In this manner, the toe valve will remain closed while the tubular string 12 is installed, cemented and pressure tested, and the toe valve will open when a pressure increase is applied after the selected number of pressure cycles are applied.

Referring additionally now to FIGS. 3A & B, more detailed cross-sectional views of an example of the downhole tool assembly 10 are representatively illustrated. The FIGS. 3A & B downhole tool assembly 10 may be used for the toe valve in the FIG. 2 well system and method, or it may be used for other purposes in other well systems and methods.

As depicted in FIG. 3A, the downhole tool 16 in this example comprises a valve that selectively permits fluid communication between the internal flow passage 22 and an exterior of the downhole tool. Ports 36 (only one of which is visible in FIG. 3A) are formed through a generally tubular outer housing 38. An inner sleeve 40 initially blocks flow through the ports 36.

The inner sleeve 40 is releasably secured against displacement relative to the outer housing 38 by shear screws 42. Seals 44, 46 straddling the ports 36 prevent leakage of fluid between the outer housing 38 and the inner sleeve 40. An atmospheric chamber 48 is isolated between the seals 44 and seals 50 carried near an upper end of the inner sleeve 40.

An annular fluid passage 52 is formed at a lower end of the inner sleeve 40, radially between the outer housing 38 and a generally tubular housing 54 of the pressure isolation assembly 14. An upper end of the housing 54 is sealingly received in the inner sleeve 40.

It will be appreciated that, if a sufficient fluid pressure is applied to the fluid passage 52, a corresponding sufficient upwardly directed force will be applied to the lower end of the inner sleeve 40 to shear the shear screws 42. The inner sleeve 40 will then be displaced upward, and will continue to displace upward (due to a difference in piston areas of the seals 44, 50), until the inner sleeve contacts a shoulder 56 formed at a lower end of an upper connector 58.

When the inner sleeve 40 displaces upward, it will no longer block flow through the ports 36. The downhole tool 16 will be open at that point. The pressure isolation assembly 14 prevents application of downhole fluid pressure 20 to the fluid passage 52, until a selected number of pressure cycles have been applied to the pressure isolation assembly, and so in this example the pressure isolation assembly prevents the downhole tool 16 from opening until after the selected number of pressure cycles have been applied.

As depicted in FIG. 3B, the pressure isolation assembly 14 includes three pressure isolation modules 18 a-c arranged in series in a sidewall of the housing 54. Other numbers of the pressure isolation modules 18 a-c may be used in other examples.

The FIG. 3B pressure isolation assembly 14 further includes a pressure reduction device 60 that functions to reduce the pressure applied to the pressure isolation modules 18 a-c downhole. Thus, only a fraction of the downhole fluid pressure 20 is applied to the modules 18 a-c in this example.

A rupture disk 62 prevents fluid communication between the flow passage 22 and a piston assembly 64 of the pressure reduction device 60, until the fluid pressure 20 exceeds a predetermined level. When the rupture disk 62 is ruptured, the fluid pressure 20 is applied to a lower end of the piston assembly 64 to thereby bias the piston assembly upward against a downwardly directed biasing force exerted by a biasing device 66 (such as, a compression spring).

Referring additionally now to FIGS. 4A-C, cross-sectional views of the pressure reduction device 60 are representatively illustrated. In these views, a pressure cycle is applied to the pressure reduction device 60 after the rupture disk 62 has been ruptured.

As depicted in FIG. 4A, the rupture disk 62 has not yet been ruptured. The biasing device 66 maintains the piston assembly 64 at its lowermost position in a housing 68 of the pressure reduction device 60.

Note that the piston assembly 64 includes a downwardly facing piston 70 and an upwardly facing piston 72. The piston 70 is exposed to pressure in an annular space 74 formed between the housing 68 and another housing 76 in which the rupture disk 62 is installed (see FIG. 3B). The downhole fluid pressure 20 is communicated to the annular space 74 when the rupture disk 62 is ruptured.

The piston 72 is exposed to an annular chamber 78 formed radially between the housing 68 and an inner mandrel 80. The chamber 78 is filled with a clean fluid (such as, a hydraulic fluid suitable for use at downhole temperatures and pressures). In this manner, debris that may be in the flow passage 22 is prevented from passing through the pressure reduction device 60 to the pressure isolation modules 18 a-c (see FIG. 3B) after the rupture disk 62 is ruptured.

As depicted in FIG. 4B, the rupture disk 62 has been ruptured. The increased fluid pressure 20 is communicated via the annular space 74 to the piston 70. As a result, the piston assembly 64 is displaced upward against the biasing force exerted by the biasing device 66.

The upward displacement of the piston 72 forces the fluid in the chamber 78 to flow through a filter 82 into a fluid passage 84 in the housing 54. The fluid passage 84 extends to the first pressure isolation module 18 a (see FIG. 3B).

The piston 70 has a smaller piston area as compared to the piston 72. As a result, the pressure applied to the chamber 78 by the upward displacement of the piston 72 is less than the fluid pressure 20 applied to the piston 70. That is, since the ratio of the piston areas of the pistons 70, 72 is less than one, the ratio of pressures acting on the pistons is greater than one.

The reduced pressure applied to the chamber 78 means that, when the fluid pressure 20 is reduced, the biasing device 66 does not have to exert as much force against the piston assembly 64 in order to return it to its initial position as it would otherwise have to exert. Similarly, biasing devices 94 of the pressure isolation modules 18 a-c described below do not have to exert as much biasing force as they would have to if the pressure were not reduced.

As depicted in FIG. 4C, the fluid pressure 20 has been decreased at the end of the pressure cycle. The biasing device 66 has displaced the piston assembly 72 back to its initial position.

Referring additionally now to FIGS. 5A-C, cross-sectional views of an example of a pressure isolation module 18 are representatively illustrated. These views show the pressure isolation module 18 in a series of configurations during a pressure cycle. The FIGS. 5A-C pressure isolation module 18 may be used for any of the pressure isolation modules 18 a-d described herein or shown in the drawings.

In this example, the pressure isolation module 18 includes a piston 86 sealingly received in a generally tubular housing 88. A seal 90 carried near an upper end of the piston 86 is sealingly engaged with a seal bore 92 formed in an upper portion of the housing 88.

A seal 98 carried on the housing 88 seals between the housing 88 and a seal bore 100 formed in the sidewall of the housing 54 (see FIG. 6 ). A fluid passage 102 is formed longitudinally through the housing 88. Initially, the piston 86 prevents flow through the fluid passage 102.

A biasing device 94 (such as, a compression spring) exerts a downwardly directed biasing force against the piston 86. The piston 86 is releasably secured against displacement relative to the housing 88 by shear pins 96.

As depicted in FIG. 5A, the rupture disk 62 (see FIG. 3B) has not yet been ruptured. The shear pins 96 prevent the piston 86 from being displaced downward by the biasing device 94.

As depicted in FIG. 5B, the rupture disk 62 has been ruptured by an increase in the fluid pressure 20 applied to the pressure reduction device 60 via the flow passage 22. As a result, a reduced fluid pressure 20 a (a fraction of the fluid pressure 20 corresponding to a ratio of the piston 70 piston area to the piston 72 piston area) is applied to the fluid passage 102 below the piston 86. Note that, if the pressure reduction device 60 is not used, then the fluid pressure applied to the fluid passage 102 will be the same as the fluid pressure 20 in the flow passage 22.

When the fluid pressure 20 a exceeds a predetermined level, the shear pins 96 shear and allow the piston 86 to be displaced upward against the biasing force exerted by the biasing device 94. Due to the upward displacement of the piston 86, the biasing device 94 is compressed in the housing 88. The piston 86 remains sealingly received in the seal bore 92.

As depicted in FIG. 5C, the fluid pressure 20 has been decreased, which also decreases the fluid pressure 20 a applied to the lower end of the piston 86. When the fluid pressure 20 a decreases to less than a predetermined level, the biasing device 94 can displace the piston 86 downwardly relative to the housing 88, until the piston is no longer sealingly received in the seal bore 92.

Note that the fluid pressure 20 a can now be communicated through the housing 88 via the fluid passage 102. The seal 90 on the piston 86 is positioned in an enlarged bore 104, which enables fluid to flow through a space radially between the seal 90 and the bore 104. Fluid passages 106 are formed in a lower portion of the piston 86 to enable fluid to flow through the lower portion of the piston.

In the FIG. 5 configuration, the pressure isolation module 18 is open and allows fluid communication between the upper and lower ends of the housing 88. If another pressure isolation module 18 is connected above the FIG. 5C pressure isolation module, then the fluid pressure 20 a can now be communicated to the pressure isolation module connected above the FIG. 5C pressure isolation module. Note that such pressure communication is not permitted in the FIGS. 5A & B configurations of the pressure isolation module 18.

Referring additionally now to FIG. 6 , a cross-sectional view of the pressure isolation module 18 c in the pressure isolation assembly 14 of the downhole tool assembly 10 is representatively illustrated. In this view, the pressure isolation module 18 c has not yet been opened. Since the pressure isolation modules 18 a-c are connected in series (see FIG. 3B), the pressure isolation module 18 c cannot be opened with a pressure cycle until the pressure isolation module 18 b is opened with a pressure cycle, and the pressure isolation module 18 b cannot be opened with a pressure cycle until the pressure isolation module 18 a is opened with a pressure cycle.

Note that a plug 108 is sealingly received in the seal bore 100 and is releasably secured with a shear screw 110. The plug 108 prevents fluid communication between the fluid passage 102 in the pressure isolation module 18 c and the fluid passage 52 in the annular space between the housings 38, 54.

When the pressure isolation module 18 c is opened in response to the application of a third pressure cycle, a lower end of the plug 108 will be exposed to the fluid pressure 20 a (see FIGS. 5B & C), or the fluid pressure 20 if the pressure reduction device 60 is not used. If a sufficient fluid pressure is subsequently applied through the open pressure isolation modules 18 a-c, the shear screw 110 will shear and thereby allow the plug 108 to be ejected upwardly out of the seal bore 100. At that point, the fluid pressure 20 a (or 20) will be communicated to the fluid passage 52 and the downhole tool 16 can be actuated by the fluid pressure as described above.

Referring additionally now to FIG. 7 , a cross-sectional view of the downhole tool assembly 10 is representatively illustrated. In this view, the pressure isolation modules 18 a-c have all been opened, the shear screw 110 has sheared and the plug 108 has been displaced upward and out of the seal bore 100, and a subsequent increase in the fluid pressure 20 has been applied to cause the inner sleeve 40 to displace upward. Flow is now permitted through the ports 38 between the flow passage 22 and an exterior of the downhole tool 16.

Referring additionally now to FIG. 8 , a cross-sectional view of another example of the downhole tool assembly 10 is representatively illustrated. In this example, the pressure reduction device 60 is not used. Instead, when the rupture disk 62 is ruptured, the fluid pressure 20 is communicated directly to the lower end of the first pressure isolation module 18 a. When all of the pressure isolation modules 18 a-c have been opened by application of three pressure cycles, the fluid pressure 20 is communicated to the plug 108. A subsequent sufficient pressure increase will cause the downhole tool 16 to be actuated due to communication of the fluid pressure 20 to the fluid passage 52.

It may now be fully appreciated that the above disclosure provides significant advancements to the art. The downhole tool assembly 10 described above allows for multiple pressure cycles to be applied before the downhole tool 16 is actuated by downhole fluid pressure 20. The number of pressure cycles can be varied by varying the number of pressure isolation modules 18 connected in series in the pressure isolation assembly 14.

The above disclosure provides to the art a pressure isolation assembly 14 for use with a pressure actuated downhole tool 16 in a subterranean well. In one example, the pressure isolation assembly 14 can comprise multiple pressure isolation modules 18 arranged in series and configured to isolate the pressure actuated downhole tool 16 from a downhole fluid pressure 20 a or 20. Each of the pressure isolation modules 18 is configured to open in response to a single pressure cycle comprising an increase in the downhole fluid pressure 20 a or 20 followed by a decrease in the downhole fluid pressure 20 a or 20.

Each of the pressure isolation modules 18 may have a first configuration (see FIG. 5A) in which pressure communication through the pressure isolation module 18 is prevented and the downhole fluid pressure 20 a or 20 is less than a first predetermined level, a second configuration (see FIG. 5B) in which pressure communication through the pressure isolation module 18 is prevented and the downhole fluid pressure 20 a or 20 is greater than the first predetermined level, and a third configuration (see FIG. 5C) in which pressure communication through the pressure isolation module 18 is permitted and the downhole fluid pressure 20 a or 20 is less than a second predetermined level.

Each of the pressure isolation modules 18 may comprise a piston 86 sealingly received in a bore 92, and a release member (e.g., shear pins 96) configured to release the piston 86 for displacement relative to the bore 92 in response to a predetermined pressure applied to the piston 86. Each of the pressure isolation modules 18 may further comprise a biasing device 94 configured to displace the piston 86 to a position in which pressure communication through the bore 92 is permitted.

The pressure isolation assembly 14 may include a pressure reduction device 60 configured to apply a fraction of the downhole fluid pressure 20 to the pressure isolation modules 18. The fraction is preferably less than one. The pressure reduction device 60 may include first and second piston areas. The fraction may be a ratio of the first and second piston areas.

A number of the pressure isolation modules 18 in the pressure isolation assembly 14 may equal a number of the pressure cycles necessary to enable actuation of the downhole tool 16 with the downhole fluid pressure 20 a or 20.

Also provided to the art by the above disclosure is a downhole tool assembly 10. In one example, the downhole tool assembly 10 can comprise: a pressure actuated downhole tool 16 configured to actuate in response to application of a downhole fluid pressure 20 to the downhole tool assembly 10; and a pressure isolation assembly 14 that isolates a fluid passage 52 of the downhole tool 16 from the downhole fluid pressure 20 a or 20. The pressure isolation assembly 14 is configured to permit communication of at least a fraction of the downhole fluid pressure 20 to the fluid passage 52 in response to application of a predetermined number of pressure cycles to the pressure isolation assembly 14. Each of the pressure cycles comprises a single increase in the downhole fluid pressure 20 followed by a single decrease in the downhole fluid pressure 20.

The pressure isolation assembly 14 may include multiple pressure isolation modules 18 arranged in series. The multiple pressure isolation modules 18 may include at least first and second pressure isolation modules 18 a,b. The first pressure isolation module 18 a may be configured to isolate the second pressure isolation module 18 b from the downhole fluid pressure 20 a or 20 until a first one of the pressure cycles is applied.

The number of the pressure cycles may be equal to a number of the pressure isolation modules 18. Each of the pressure isolation modules 18 may be configured to open in response to application of a respective one of the pressure cycles. Each of the pressure isolation modules 18 may be configured to open in response to the decrease in the downhole fluid pressure of the respective one of the pressure cycles.

The pressure isolation assembly 14 may include a pressure reduction device 60 configured to apply the fraction of the downhole fluid pressure 20 to the downhole tool 16. The fraction may be less than one.

Also described above is a method of actuating a downhole tool 16. In one example, the method comprises: determining a number of downhole fluid pressure cycles to apply in a subterranean well to enable actuation of a downhole tool 16; installing a number of pressure isolation modules 18 in a pressure isolation assembly 14, the number of pressure isolation modules 18 corresponding to the number of pressure cycles; deploying the downhole tool 16 and the pressure isolation assembly 14 into the well while the pressure isolation assembly 14 isolates a fluid passage 52 of the downhole tool 16 from downhole fluid pressure 20 a or 20; and applying the number of pressure cycles in the well, the pressure isolation assembly 14 thereby permitting communication of at least a fraction of the downhole fluid pressure 20 to the fluid passage 52.

The installing step may include connecting the pressure isolation modules 18 in series in the pressure isolation assembly 14.

The applying step may include opening each of the pressure isolation modules 18 in response to application of a respective one of the pressure cycles.

The applying step may include opening each of the pressure isolation modules 18 in response to a downhole fluid pressure decrease of the respective one of the pressure cycles.

Each of the pressure cycles may comprise a single downhole fluid pressure increase followed by a single downhole fluid pressure decrease.

The applying step may include applying the fraction of the downhole fluid pressure 20 to the pressure isolation modules 18, the fraction being less than one.

Although various examples have been described above, with each example having certain features, it should be understood that it is not necessary for a particular feature of one example to be used exclusively with that example. Instead, any of the features described above and/or depicted in the drawings can be combined with any of the examples, in addition to or in substitution for any of the other features of those examples. One example's features are not mutually exclusive to another example's features. Instead, the scope of this disclosure encompasses any combination of any of the features.

Although each example described above includes a certain combination of features, it should be understood that it is not necessary for all features of an example to be used. Instead, any of the features described above can be used, without any other particular feature or features also being used.

It should be understood that the various embodiments described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of this disclosure. The embodiments are described merely as examples of useful applications of the principles of the disclosure, which is not limited to any specific details of these embodiments.

In the above description of the representative examples, directional terms (such as “above,” “below,” “upper,” “lower,” “upward,” “downward,” etc.) are used for convenience in referring to the accompanying drawings. However, it should be clearly understood that the scope of this disclosure is not limited to any particular directions described herein.

The terms “including,” “includes,” “comprising,” “comprises,” and similar terms are used in a non-limiting sense in this specification. For example, if a system, method, apparatus, device, etc., is described as “including” a certain feature or element, the system, method, apparatus, device, etc., can include that feature or element, and can also include other features or elements. Similarly, the term “comprises” is considered to mean “comprises, but is not limited to.”

Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the disclosure, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to the specific embodiments, and such changes are contemplated by the principles of this disclosure. For example, structures disclosed as being separately formed can, in other examples, be integrally formed and vice versa. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the invention being limited solely by the appended claims and their equivalents. 

What is claimed is:
 1. A pressure isolation assembly for use with a pressure actuated downhole tool in a subterranean well, the pressure isolation assembly comprising: multiple pressure isolation modules arranged in series and configured to isolate the pressure actuated downhole tool from a downhole fluid pressure, each of the pressure isolation modules being configured to open in response to single pressure cycle comprising an increase in the downhole fluid pressure followed by a decrease in the downhole fluid pressure.
 2. The pressure isolation assembly of claim 1, in which each of the pressure isolation modules has a first configuration in which pressure communication through the pressure isolation module is prevented and the downhole fluid pressure is less than a first predetermined level, a second configuration in which pressure communication through the pressure isolation module is prevented and the downhole fluid pressure is greater than the first predetermined level, and a third configuration in which pressure communication through the pressure isolation module is permitted and the downhole fluid pressure is less than a second predetermined level.
 3. The pressure isolation assembly of claim 1, in which each of the pressure isolation modules comprises a piston sealingly received in a bore, and a release member configured to release the piston for displacement relative to the bore in response to a predetermined pressure applied to the piston.
 4. The pressure isolation assembly of claim 3, in which each of the pressure isolation modules further comprises a biasing device configured to displace the piston to a position in which pressure communication through the bore is permitted.
 5. The pressure isolation assembly of claim 1, further comprising a pressure reduction device configured to apply a fraction of the downhole fluid pressure to the pressure isolation modules, the fraction being less than one.
 6. The pressure isolation assembly of claim 5, in which the pressure reduction device comprises first and second piston areas, and the fraction is a ratio of the first and second piston areas.
 7. The pressure isolation assembly of claim 1, in which a number of the pressure isolation modules in the pressure isolation assembly equals a number of the pressure cycles necessary to enable actuation of the downhole tool with the downhole fluid pressure.
 8. A downhole tool assembly, comprising: a pressure actuated downhole tool configured to actuate in response to application of a downhole fluid pressure to the downhole tool assembly; and a pressure isolation assembly that isolates a fluid passage of the downhole tool from the downhole fluid pressure, the pressure isolation assembly being configured to permit communication of at least a fraction of the downhole fluid pressure to the fluid passage in response to application of a predetermined number of pressure cycles to the pressure isolation assembly, each of the pressure cycles comprising a single increase in the downhole fluid pressure followed by a single decrease in the downhole fluid pressure.
 9. The downhole tool assembly of claim 8, in which the pressure isolation assembly comprises multiple pressure isolation modules arranged in series.
 10. The downhole tool assembly of claim 9, in which the multiple pressure isolation modules comprise at least first and second pressure isolation modules, the first pressure isolation module being configured to isolate the second pressure isolation module from the downhole fluid pressure until a first one of the pressure cycles is applied.
 11. The downhole tool assembly of claim 9, in which a number of the pressure cycles is equal to a number of the pressure isolation modules.
 12. The downhole tool assembly of claim 9, in which each of the pressure isolation modules is configured to open in response to application of a respective one of the pressure cycles.
 13. The downhole tool assembly of claim 9, in which each of the pressure isolation modules is configured to open in response to the decrease in the downhole fluid pressure of the respective one of the pressure cycles.
 14. The downhole tool assembly of claim 8, in which the pressure isolation assembly further comprises a pressure reduction device configured to apply the fraction of the downhole fluid pressure to the downhole tool, the fraction being less than one.
 15. A method of actuating a downhole tool, the method comprising: determining a number of downhole fluid pressure cycles to apply in a subterranean well to enable actuation of a downhole tool; installing a number of pressure isolation modules in a pressure isolation assembly, the number of pressure isolation modules corresponding to the number of pressure cycles; deploying the downhole tool and the pressure isolation assembly into the well while the pressure isolation assembly isolates a fluid passage of the downhole tool from downhole fluid pressure; and applying the number of pressure cycles in the well, the pressure isolation assembly thereby permitting communication of at least a fraction of the downhole fluid pressure to the fluid passage.
 16. The method of claim 15, in which the installing comprises connecting the pressure isolation modules in series in the pressure isolation assembly.
 17. The method of claim 15, in which the applying comprises opening each of the pressure isolation modules in response to application of a respective one of the pressure cycles.
 18. The method of claim 17, in which the applying comprises opening each of the pressure isolation modules in response to a downhole fluid pressure decrease of the respective one of the pressure cycles.
 19. The method of claim 15, in which each of the pressure cycles is a single downhole fluid pressure increase followed by a single downhole fluid pressure decrease.
 20. The method of claim 15, in which the applying comprises applying the fraction of the downhole fluid pressure to the pressure isolation modules, the fraction being less than one. 